Here we are again, dreaded smog time!

Today I smogged my '92 400E with 217,000 miles and it failed! What a pain in the ass! Now comes the fun of getting it to pass, and anyone who's had to deal with this knows just how great it can be.

I've searched past posts and have a fairly good idea of what the problem might be, but since there's some members of this forum who seem to be experts on this subject I thought why not see what you've got to say.

So a little info. about my car and the smog test results. As mentioned above, I have a 1992 400E with just over 217,000 miles, the car runs really well for it's age and mileage. Last smog test passed fairly well as I remember. The check engine light comes on occasionally, I believe the code it brings up refers to a communication issue between two of the computers, when I reset it usually stays off for about 2-4 months before coming back on. The cat. has that special smell only at certain times, like when going up hill under load and whatnot. Since I've owned the car I haven't done any work to any of the smog related parts. I think that the cat. is the culprit, but the O2 sensor might be to blame as well, it's only guess though.

Here are the test results:

15 MPH Test

RPM: 1350 - CO2: 14.1 - O2: 0.6
HC(PPM) MAX: 105 - GP: 280 - MEAS: 232
CO(%) MAX: 0.69 - GP: 2.19 - MEAS: 0.59
NO(PPM): MAX: 757 - GP: 1943 - MEAS: 2356

25 MPH Test

RPM: 1361 - CO2: 15.1 - O2: 0.2
HC(PPM) MAX: 80 - GP: 230 - MEAS: 102
CO(%) MAX: 0.56 - GP: 2.06 - MEAS: 0.15
NO(PPM) MAX: 696 - GP: 1743 - MEAS: 417

So, as you can see it passed some tests fine and others it just failed, and badly. If anyone as any input from these readings on what the problem might be I'm all ears. If it ends up that the whole system needs replacing I'll probably just end up buying another car, but I really don't want to do that since I love this car!

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1992 Mercedes-Benz 400E
2002 Mercedes-Benz ML500

You have high NO which indicates the EGR system is not flowing to reduce combustion temperatures on your first 15mph test..

High combustion temperatures produce high NO.
You need to find out if the vacuum hoses and the EGR valve are functioning.

CO indicates your cat's working okay but fuel mixture a little rich at low speed which might be a lazy O 2 sensor..
Was this an Enhanced test or a Basic. ?

We don't have Smog Checks here, but I think we ought to.


.

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[http://languageandgrammar.com/2008/01/14/youve-got-problems-not-issues/ ]

"A liberal is someone who feels they owe a great debt to their fellow man, which debt he proposes to pay off with your money."

I don't know which test it was. I had to go to a test only station which involves a dino in the process.

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1992 Mercedes-Benz 400E
2002 Mercedes-Benz ML500

Clean out your EGR pipes, they get clogged. Replace the injector seals, rubber vacuum hoses/elbows and plastic vacuum lines. Check the catalytic converter to make sure it's not damaged.

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Regards

Warren

Currently 1965 220Sb, 2002 FORD Crown Vic Police Interceptor

Had 1965 220SEb, 1967 230S, 280SE 4.5, 300SE (W126), 420SEL

ENTER > = (HP RPN)

Not part of the in-crowd since 1952.

I agree...clogged EGR tube last year got my 300E to fail for the first time!

After that, drive the s#it out of the car on the highway for a few days prior to retest.

There is some stuff you can buy in a tiny jug called de-carbonizer, that is sort of a "cheat sheet" way to help push along your emission results. Pour it into your tank, then drive around enough to get your cat heated up sufficiently before you get your smog test done.

Mine barely passed after that (didn't get to drive the living hell out of it before the test), but that's all you're gunning for anyway!

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2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car

check out my thread

Smog check caught up with me


glenmore
1991 300CE
2000 C280
1990 LS400

Well it seems to me as if it's got to be the EGR valve and tube. I think I'll take a look at it and see what I can find.

As for the cat being the issue I don't think it's the issue anymore. I was under the car recently and inspected the whole exhaust system included the cat, from the outside there's absolutely no damage, not even any rust!

I'll let you all know what I find.

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1992 Mercedes-Benz 400E
2002 Mercedes-Benz ML500

>>

I hope you do not assume a cat can be diagnosed as OK by looking at the outside of it....

Oh definitely, but to not see any damage outside makes me feel better.

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1992 Mercedes-Benz 400E
2002 Mercedes-Benz ML500

I'm going to send an application into the consumer assistance program and will hopefully get this fixed for free.

As for the retest, it's free, but for how long? Do I only have a certain amount of time that it's free? And, is the free retest free by law?

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1992 Mercedes-Benz 400E
2002 Mercedes-Benz ML500

My re-test needed to be done within ten days of the initial test. I don't know if it is a law, or the stations option.

I sent in my CAP application on 4/25 and have not heard back yet.

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1993 190E 2.6 135k
1989 Ford Thunderbird SC 5 Spd 79K

I took a shot at a used EGR valve on eBAY; It cost about $30 and has worked like a charm for over a year so far.

DG

Well, I was approved for the CAP program which is good news. They sent a list of mechanics that participate in the program, of which I must choose one and am required to go to if I want CAP to pay for the repairs.

I took my car in earlier this week to have it worked on, the mechanic told me that the odds of my car, or any car going over the CAP limit ($500) is rare and that my car should be only in for a day or two. After a full analysis of my car it seems as if there's more wrong with it then right.

First, he said that the vehicle didn't have enough power to complete the smog test, he said he tried 4 times and no luck. Finally on the fifth time it made it through. He noted that the vehicle has hardly any power and probably has back up cats. Hmmm...

Second, he said that the engine has a misfire and whats causing it is a bad coil, so that will need to be replaced. Hmmm...

Third, just a lot of random small issues, which may or may not be related to my vehicle failing smog. Hmmm...

As for the first and second issues, I personally don't think the car is underpowered at all, I've driven several versions of my car and they all had the same behavior. When I originally had it smogged and it failed I was there for the test and it had no issues. My car has ran the same, and has had the same power for well over 100k miles that I've owned it. I don't doubt that the cats might be bad, but if they are I'm not will to throw down $1600 for both of them, so that problem will stay if it even exists. As for the bad coil, since the engine only has two coils, one for each cylinder bank, I would think that if there was a bad coil the engine wouldn't run, or would run very badly. The engine runs better than ever and is silkly smooth. I really think that he is wrong and it all my be BS, but he has a good reputation and seems like a good guy, but who knows. I really have no choice since it's done through the CAP.

I personally think that the EGR valve and oxygen sensor should be replaced, but he doesn't think any of those parts are bad. Bottom line is that I told him repairs cannot go over the $500 CAP limit so whatever he does I really hope will be the best for the car. Even if the car still doesn't pass smog after this I'll be able the get a smog exemption waiver and be able to register the car, but I would like the have it pass if possible. I've done all the work on this car myself since I've owned it and really know it inside out, I really hope all my worrying is for nothing and I'm wrong, guess we'll see.

What a hassle! Ahhhhhhh

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1992 Mercedes-Benz 400E
2002 Mercedes-Benz ML500

Don't change any parts till you get the car tested hot.Those numbers are from a cold cat.That is why the 25mph test is so much better.
I work as a smog tech for a cap shop.
Do not change your cat unless it is broken,use only direct fit o2 sensor if you change o2.NO GENIRIC 02 SENSOR.
Bring car in for a new test and sit in the car with the motor running at about 1,200 rpm.
Car will pass no problem.If a cap shop works on it you may end up with a geniric cat converter,which may only pass one time,as in replace cat at each new smog. If car fails hot then at least you will have correct fail numbers.
All the Mercedes I smog at work will pass hot with maybe only a new Mercedes 02 sensor
Rich

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88 300E White, sold 9-04
88 190E Black 2.3 sold
90 300CE White, Grey sold 12-24-04
92 400E White,Grey Sold 5-06
90 300CE 91K Signal Red,Black Sold 2007
1989 300CE Smoke silver,Tan Sold 1-08
1993 300E 3.2 M104 motor
1991 300CE White,Grey
1994 E420 beautiful car,gone to new home
1994 E320 Smoke an Parchment.Beautiful car